What happened
On 20 March 2021, a Boeing 737-40 and registration PK-YSF, operated by Trigana Air Service, was conducting a scheduled cargo flight from Halim Perdanakusuma International Airport in Jakarta. Shortly after departing Runway 24, the crew identified a failure in the right engine. The flight crew requested to return to the airport to perform an emergency landing.
During the approach, the aircraft was configured with flap 15 and was operating at a weight of approximately 131,000 lbs. Upon touchdown at 11:26 LT, the aircraft experienced a high vertical acceleration of 1.79 G. Shortly after contact with the runway, the right main landing gear failed, causing the aircraft to veer off the runway onto the left shoulder. The aircraft came to a stop approximately 2,200 meters from the start of the runway. While there were no fatalities or injuries, the aircraft sustained substantial damage, and smoke was observed emanating from the left side of the airframe.
The investigation
The KNKT examined flight data from the Flight Data Recorder (FDR) and audio from the Cockpit Voice Recorder (CVR). The investigation focused on the sequence of engine parameter changes following takeoff, the execution of emergency checklists, and the flight path during the final approach. Investigators also reviewed the aircraft's weight and balance, noting that the landing weight exceeded the maximum landing weight of 121,000 lbs. Additionally, the investigation looked into the crew's response to Ground Proximity Warning System (GPWS) alerts and the management of fuel imbalance during the emergency descent.
Findings
- The right engine experienced a significant drop in N1 and EGT levels shortly after takeoff, leading to a total shutdown approximately eight minutes into the flight.
- The crew failed to properly execute the Quick Reference Handbook (QRH) procedures, as evidenced by delays in reducing the throttle and switching off the PACK switch.
- A significant fuel imbalance of 1,000 lbs was reached, hitting the maximum allowable limit.
- The flight crew did not correct the flight path in response to multiple "GLIDESLOPE" and "TOO LOW TERRAIN" EGPWS warnings during the approach.
- The approach briefing did not adhere to the required Threat and Error Management (TEM) standards outlined in the operator's manual.
Safety action
Following the incident, Trigana Air Service implemented measures to improve pilot safety awareness and proficiency. The airline also initiated a working order to perform engine run-up tests across its entire B737 fleet to monitor engine performance and identify potential systemic issues.